1. Field of the Invention
This invention relates to an enclosure assembly for use on elongate cylindrical objects.
More specifically, the invention is directed to sheathing sleeves intended for application over cable splices, or cable ends, in medium- to high-voltage power lines where the high electric potentials involved, being on the order of tens or hundreds kV in magnitude, require that air inclusions be totally absent from between the sleeve inner surface and the outer surface of a cable to be sheathed.
It is understood, however, that the enclosure assembly of this invention may be also employed for applications other than the above-outlined one, for instance over cylindrical objects of various description--such as pipes, rods, bars, and the like--e.g. to provide local protection against corrosion or else.
2. Description of the Related Art
As is known, in splicing electric cables together, it is common practice to remove locally protective and insulating members from around the conductor of either cable, at the ends of the cables to be spliced together, for connection to the conductor of the other cable.
After optionally filling with appropriate materials (jointing compounds, self-amalgamating tapes, or the like) the gaps left from the removal of insulative and/or protective members, the spliced bare ends of the two cables are covered with a sheathing sleeve of an elastomer material which provides the necessary protection and insulation for proper performance of the splice.
The elastomer sleeve is preliminarly fitted, in a condition of elastic expansion, over a tubular cylinder body made of a rigid plastics material to be engaged around either cable prior to splicing.
Subsequently, after the conductors have been spliced to each other, the tubular body is removed from the elastomer sleeve, thereby allowing the sleeve to shrink elastically about the cables at the splice.
A prior art device, as disclosed in Patent GB 1,292,608, provides a support consisting of a tubular cylinder body whereover an elastic covering is fitted. The tubular body is formed with a helical groove around its outer surface. In this way, a continuous strip is substantially created on the tubular cylinder body in the form of a plurality of turns laid consecutively and being set close against one another along a weakening line of reduced thickness which is defined at the bottom of the helical groove.
By exerting a pull force on a free end portion of the strip which extends from one of the turns at the tubular body ends and longitudinally through the body, the turns are progressively separated along said weakening line. Thus, the tubular cylinder body can be removed from the elastic covering by a simple manual operation requiring no special puller.
U.S. Pat. No. 4,503,105 provides a helical groove cut in the thickness of the tubular body. The individual turns are interconnected by longitudinal bridge formations on the tubular body interior whose thickness is only partly affected by the helical groove depth.
European Patent EP 0 291 203 discloses instead a tubular body wherein a plurality of through-going cutouts, set closely apart in a helical pattern, are formed using a suitable tool operated on the outer surface of the cylindrical body.
A further known support, shown in U.S. Pat. No. 4,389,440, has the tubular cylinder body formed by a band-like element which is wound helically into a plurality of side-by-side turns bonded to one another. Here again, by exerting a pull force on a free end portion of the band-like element laid longitudinally through the tubular body, the tubular body is caused to collapse as the turns come progressively apart.
According to the invention, it has been observed that in some instances, such as when sleeves carried on tubular supports are fitted over electric cable splices--particularly in medium voltage applications--the space requirements for the free end portion inside the tubular support may have to be minimized.
In fact, a single size sleeve and respective tubular support to accommodate a range of cable outside diameters is a particularly desirable feature in such applications; for this purpose, to avoid the need for extra radial expansion of the elastic sleeve, the gap between the outer surface of the largest anticipated diameter cable and the inner surface of the tubular support should be kept small. The minimum size of said gap is dictated by the space requirements of the free end portion inside the tubular body.
In fact, in order to fit the sleeve over such cylindrical objects as the elements of a splice between two electric cables, one of the cables must be introduced into the tubular support carrying the sleeve by sliding it over the outer sheath.
At that stage, between the cable and the outer surface of the tubular support there must be left at least a corresponding space to the overall radial dimension of the band-like extension within the tubular support. It has been found, moreover, that a highly flexible free end portion is a specially important feature.
In fact, some regions of the cable splice are covered or filled with self-amalgamating tapes, compounds, greases, or the like, i.e. with soft materials liable to be harmed or deformed by rubbing contact with harder elements, specifically the free end portion.
In addition, the surface of the cable insulator may also become scored or damaged from rubbing contact with a harder element, such as the free end portion, to leave a region prone on triggering surface electric discharges in operation of the joint.
The free end portion, when bent over and led through the tubular support interior, forms a loop with origin in its area of separation from the intact portion of the support, which represents some bulk within the tubular support.
The size of the loop, and hence its space requirements inside the tubular support, will be the larger, the lower is the flexibility of the free end portion.